The present invention relates to a device for displaying electrical signals of the periodic and/or synchronisable type.
In particular the present invention relates to a display device advantageously usable to effect analysis of electro-cardiographic signals over a long period.
As is known, the long term analysis of electrocardiographic signals is a diagnostic technique used both in coronary treatment units and in dynamic electrocardiography. In the first case it is necessary continuously to supervise the evolution of the electrocardiographic trace of patients at high risk in order to allow a rapid recognition of dangerous electrocardiographic phenomena. In the second case electrocardiographic traces recorded over many hours, even for an entire day, are analysed by means of a unit carried by patients who follow their normal activities; in this way it is possible to identify incidents which, because they manifest themselves in an unpredictable and sporadic manner cannot be detected by conventional electrocardiographic examination.
Given the enormous quantity of information to be interpreted in both the above mentioned cases, instruments have been provided to facilitate the diagonsis by the doctor. In particular, a first group of commercially available instruments perform, in a substantially automatic manner, analyses of electrocardiographic signals, thereby excluding the doctor from the recognition and evaluation of individual incidents. A second group of instruments, also currently commercially available, display the electrocardiographic trace on a monitor, leaving the analysis entirely to the doctor. Systems of the second group have therefore various limitations. First of all they present either only a few electrocardiographic cycles in a sequential and non-synchronised manner, or else a single synchronised electrocardiographic pattern. Given the restricted period of time within which the electrocardiographic pattern appears on the screen, the identification of a possible anomaly is particularly difficult. Even more difficult is the establishment of the correlation between adjacent cardiac cycles; such correlations are in fact very important for identifying the occurrence of slow morphological variations and variations in the rythm.
For the purpose of obviating some of the above-mentioned disadvantages there has also been set up a technique known as "contourograph" on the basis of which adjacent cardiac cycles are recorded in a superimposed and suitably spaced manner on a roll of paper. In this way it is certainly easier to identify the occurrence of the said slow morphological variations and variations in rythm, but it is likewise apparent that a system of this type is entirely impractical when it is desired to analyse traces recorded over more than twentyfour hours because of the time required for the doctor to examine the whole of the electrocardiographic patterns.